Summary: Effect of Number of Fractionating Trays
on Reactive Distillation Performance
Muhammad A. Al-Arfaj and William L. Luyben
Process Modeling and Control Research Center, Dept. of Chemical Engineering, Lehigh University, Bethlehem, PA 18015
Sneesby et al. recently suggested that adding trays in the stripping and rectifying sec-
tions of a reacti容 distillation column can degrade performance. This effect, if true, is
not only counterintuiti容, but 容ry disturbing because it suggests that the design of reac-
ti容 distillation columns cannot use conser家ti容 estimates of tray numbers, that is, we
cannot simply add excess trays, as in con容ntional distillation. The problem is com-
pounded by the uncertainty in 家por liquid equilibrium data and tray efficiencies. This
implies that de容loping reacti容 distillation columns would require extensi容 experimen-
tal work at the pilot-plant and plant stages to find the numbers of stages offering the
best performance. Such a scenario would mean long and expensi容 de容lopment pro-
grams. This article explores the effect of the number of trays in the rectifying andror
( )stripping sections of reacti容 catalytic distillation columns. Three reacti容 distillation
systems are used: an ideal hypothetical system, the ETBE system, and the methyl ac-
etate system. Contrary to the published results, it is demonstrated that additional trays
do not degrade performance. Two degrees of freedom a家ilable in all cases must be
carefully chosen for fair comparisons.
Introduction